1. Field of the Invention
The present invention relates to a motor driven camera in which a plurality of mechanisms in the camera are driven by a motor.
2. Description of the Prior Art
In a modern motor driven camera, there is a tendency to use a motor direct drive system not only to wind up a film but also to drive a mirror, a stop and charge a shutter, because the direct drive system is superior with respect to efficiency and simplification of construction, to an indirect drive system in which a spring is charged by an electric motor and a charge of the spring is used to drive the mechanisms.
However, when it is desired with such a camera to change a time required to one frame photographing by changing a rotating speed of the motor, the following problem is encountered.
In a camera which directly drives a member for determining a stop aperture by the motor, a displacement speed of the member changes as the motor rotating speed changes. The aperture determining member is latched by a latch mechanism when it reaches a position corresponding to a desired stop aperture in the course of displacement from a position corresponding to a maximum stop aperture to a position corresponding to a minimum stop aperture prior to shutter operation. As the displacement speed of the aperture determining member increases, it becomes difficult to accurately stop the member at the desired position and hence an error occurs in the stop control.
In a single lens reflex type motor driven camera which directly drives a mirror drive system by the motor, as the motor rotating speed increases, a mirror reciprocating speed also increases. As a result, a shock caused when the mirror is raised and stopped at a photographing position increases. This causes a vibration of the camera and results in a low quality picture.
In a camera which directly drives mechanisms which are driven during the time period between the depression of a release button and the start of run of the shutter (stop drive system, mirror drive system, auto-focusing lens drive system, etc.) by the motor, as the motor rotating speed changes, a start timing of the exposure of the film also changes. That is, the time period from the depression of the release button to the start of the run of the shutter changes. As a result, a user cannot determine the exposure timing and hence a picture which is different from an intended one is produced.